Variable capacity pump



w. R. EAMES, JR

VARIABLE CAPACITYPUMP Oct. 3, 1961 Filed Aug. 15, 195.6

2 Sheets-Sheet l Fig] INVENTO WALTER R. EAME v MM f7.4

A TTORNE YS Oct. 3, 1961 w. R. EAMES, JR

VARIABLE CAPACITY PUMP 2 Sheets-Sheet 2 Filed Aug. 13, 1956 INVENTOR.WALTER R. EAMES JR.

MMP@

mm: O

A TTORNE YS United States Patent O 3,002,461 VARIABLE CAPACITY PUMPWalter R. Eames, Jr., Royal Oak, Mich., assignor to Eaton ManufacturingCompany, Cleveland, Ohio, a corporation of Ohio Filed Aug. 13, 1956,Ser. No. 603,581 Claims. (Cl. 10S- 11) In many applications requiringpressurized hydraulic fluid to perform work in a hydraulic circuit, thevolume requirements vary greatly. To satisfy the demand in such asystem, a variable capacity pump is ordinarily used. This results in apump which, by necessity, is more complicated than a constantdisplacement type pump.

This invention relates to the accomplishment of the :function of avariable displacement type pump by using la constant displacement pumpwith a novel valving arrangement.

An object of this invention is to provide a constant displacement pumpwith a novel valvingarrangement to replace a variable displacement pump.

A further object is to provide a pump having multiple pumping strokesper pump cycle.

These and other objects and advantages will become more yapparent fromthe following detailed description of the device and from theaccompanying drawings.

FIGURE 1 schematically illustrates a pump and novel control Itherefor.

FIGURE 2 shows the control illustrated in FIGURE l in a dilierentoperating position.

FIGURE 3 is a modiiication of the control system.

FIGURE 4 illustrates the modication shown in FIG- URE 3 in a diiierentoperating position.

This device is comprised of a lluid control system corn-v prising asingle pump having at least two pumping chambers ot equal or unequalcapacity, depending upon the particular application of the structure orof a plurality ot pumps having single or multiple pumping chambers withequal or unequal capacity, depending upon the application of thestructure. For convenience, the device will be described utilizing asingle pump with two pumping chambers of unequal capacity. The pumpingchambers are in communication with a -fluid reservoir which provides thenecessary supply of oil to the pump. In a structure utilizing twopumping chambers, the communication between the reservoir and one of thechambers is provided with :a check valve which allows flow to thechamber from the reservoir but prevents reverse flow and this lirstchamber is also provided with a dischargecommunication to an out-putline. The second pumping chamber is provided with similar communicatinglines to the reservoir and the output line except that there is no checkvalve provided in the intake line ttor the second chamber. A valve meansis provided having a plunger which is connected to the discharge frombot-h chambers in the output line, tendingto move the valve in onedirection, and spring means opposing this iiuid force. When the valveplunger is longitudinally moved a'certain IamountV in response to fluidpressure, the output from bothl o-f said pump chambers is communicatedby a `first bypass line means to the intake of the hist mentioned `plumpchamber. When the valve -plunger is moved further in the same direction,the combined output of the pump is communicated to the intake of both ofsaid pump chambers by said ii-rstbypass line anda second bypass lineconnected to said valve and said second mentioned pump chamber. Thebypass return tlow i-n the iirst mentioned line is prevented fromreturningto the reservoir by the, previously mentioned check valve.Therefore,`when the valve is moved so that the lirst bypass Lline and atleast a pontion of the second bypassline are incominunic'atdn with' the'combined outputl of the ICC pump, a volume equal to the output of theiirst chamber is merely shunted back to the first chamber with noresulting loss of work except -for irictional line losses. When the pumpoutput is decreased or the output requirement is increased, the valve isclosed in response to the diiferential of the spring torce and reduceddischarge pressure and the Ifull capacity of the pump is discharged tothe output line. If for any reason the output requirement is greatlydiminished or the pump output is greatly increased, the pressure in theoutput line increases and the valve is completely opened which resultsin a bypass of the Afull capacity of the pump back to the pumpingchambers. A communication is provided between the wonk performing deviceand the reservoir to provide a return for the fluid.

It is to be noted that a pump having more than two pumping chambers canbe utilized. Ii, Ifor example, a unit having four pumping chambers isused and it is desired to be able to motor one, two, o-r three of the.chambers, check valves are placed in the communicating lines between thereservoir and the intake means to each of the chambers to be motored toprevent flow of uid back to the reservoir.

Referring to the drawing for a more detailed description of theinvention, the iluid device 10 4is provided with a rotary pump 12 havinga rotor 14 and a housing 16. A rotary pump is illustrated but theinvention is not limited to this type pumping structure. A pressurerelief valve .18 communicates with the discharge and inrta'ke of thepump 12 in a manner which will be described in detail in the followingdescription.

The pump 12 is provided with a relatively large ca pacity chamber 20 anda smaller capacity chamber 22. A reservoir 24 furnishes fluid to thehigh capacity pump chamber by'means of fluid conduits 26, 28, and 30. Acheck valve 32 is interposed in conduit 28 which allows lflow Ifrom thelarge capacity chamber to the reservoir and -t-he small capacity chamberis furnished with fluid from the reservoir by means of lluid conduits26, 34, and 36. The valve 18 is provided with a pair of bypass ports,318 and `40, the port 38 communicating with the conduit 36 by means of aconduit 412 and bypass port 40 communicating with lconduit 30 by meansot conduit 44.

A conduit 46 is connected at one end to the discharge side of the lowcapacity chamber 22 and is connected at the other end to chamber 48 ofvalve 18.. A conduit 50 is connected at one end to the discharge of thehigh capacity chamber 20 and at the other end to the conduit 46 so thatthe :discharge `from both the large capacity and the small capacitychambers is communicated to the valve chamber `48. The remainder of thevalve structure 18 is comprised of a piston 52 having an end portion incommunication with the chamber 48 `and a compression spring 54 actingagainst the piston 52 yand reacting against an adjustable plug 56. Anoutput port 58 is connected to the chamber 48 of valve 18 and providesacomrnunication between the control system 10 and the working system(notshown). Obviously, the output por-t can be located at any point inthe discharge conduit 46 and is shown formed vin vthe valve housingmerely for a convenience and is not "limited to the exact location shownin the drawing. Also, there is a communication between the Vexhaust sideof the working system and the reservoir `to provide a return'means foruid to the reservoir. The

`wise direction, fluid from the sump is communicated both to the largecapacity chamber and the small capacity chamber. Fluid under pressure isthen discharged into the conduits 46 and 50 which jointly communicatewith thvalve chamber 48 and thence to the output port 58.

When the discharge requirements to the working system are such that thefull output pressure of the pump is required, the piston 52 of controlvalve 18 will remain in the position shown in FIGURE 1. At this time,the total pressure of the low capacity and high capacity chamber isdirectly communicated to the output port 58 with no bypass of pressurefrom either of the working chambers back to the pump. When the dischargerequirements are decreased or there is a substantial increase in pumpflow, a pressure rise in the discharge line and in the chamber 48results in the movement of piston 52 of valve 18 to a position wherein`the bypass port 40 is uncovered. The combined pump discharge is now incommunication with both the output conduit 58 and the bypass conduit 44which bypasses a portion of the output of the combined pump dischargeback to the large capacity chamber. At this time, there is no motoringeffect but when the requirements are lagain reduced until piston 52moves to a position establishing at least a partial communicationbetween output conduit 58 and bypass conduit 42, the discharge from thelarge capacity chamber is bypassed or recirculated back to the largecapacity chamber resulting in a motoring of the large capacity chamber.Under this operating condition, the high capacity chamber is in amotoring condition, but most irnportant, this motoring does not resultin any power loss except for line losses, since the discharge from thelarge capacity chamber is communicated back to the intake side of thelarge capacity chamber. If the discharge requirement falls below apredetermined minimum, the piston 52 moves further upward, as shown inFIGURE 2, resulting in greater communication of the bypass port 38 withthe chamber 48. Consequently, the total discharge of the high capacitychamber and a portion of the discharge of the low capacity chamber, lessline losses, is bypassed back to the intake of both chambers of the pumpwith `the high capacity chamber being motored and the remaining portionof the low capacity chamber output, less line losses, being returned tothe low capacity chamber input and the reservoir.

*FIGURE 3 illustrates a modification of the control valve. A valve 118is provided with a valve body 155, a piston 152, a compression spring154 interposed between the piston 152 and the adjustable plug 156 and apair of bypass ports 138 and 140 communicating by conduit means with thelow and high capacity chambers, respectively. An orice 160 is providedin the piston 152 so that fluid flow from the discharge side of thelarge capacity chamber and the small capacity chamber flows through theorifice into the discharge conduit 158. This modied structure operatesin the following manner.

When the pump rotor is rotated, iiuid from the reservoir 124 iscommunicated to both the large capacity chamber 120 and the smallcapacity chamber 122. Fluid under pressure is then discharged into thedischarge conduits 146 and 150 which communicate with the valve chamber148, orilice 160, and the discharge conduit 158.

When the iiow requirements to the system are such that the discharge ofthe pump does not exceed those requirements, piston 152 of the controlvalve 118 will remain in the position shown in FIGURE 3. At this time,the combined iiow of the small capacity chamber and the large capacitychamber is directly communicated to the output conduit 158 and there isa maximum permissible pressure drop across orifice 160 with no bypass ofuid from either of the working chambers back to the pump. When thedischarge of the pump is increased above the requirements of the workingsystem or the requirements of the working system are reduced, How acrossthe oriiice is increased and there is a consequent increase in pressuredrop across the orifice which results in a movement of the valve to aposition in which bypass port 140 is uncovered. The combined pumpdischarge is now in communication with both the output conduit 58 andthe bypass port 140 which results in a bypass of a portion of the outputof the combined pump discharge back to the large capacity chamber. Atthis time, there is no motoring but when the flow requirements are againreduced until piston 152 moves to a position establishing at least apartial communication between output conduit 158 and bypass conduit 142,the discharge from the large capacity chamber is bypassed orrecirculated back to the large capacity chamber with no resulting lossof work except for frictional line losses. VUnder this condition, thelarge capacity chamber is motoring. It is obvious therefore, that thismodification of the device is responsive to ow rather than beingpressure responsive. If the discharge of the pump increases further,piston 152 of valve 118 moves further upwardly (as viewed in FIG- URE 4)resulting in greater communication of bypass port 138 with the outputconduit. Consequently, an increased quantity of flow `from the pump isbypassed to the intake of the low capacity chamber of the pump.

It is obvious that the ratio of the capacity of the large capacitychamber and the small capacity chamber can be varied to obtain anypercentage of reduction in fiow that is desired. For example, in use ina transmission, a small basic flow is required for leakage and a muchhigher flow is necessary when effecting the movement of one or moreclutches. In such an application, the structure disclosed herein wouldshift into high range to lill the clutch rapidly and then drop to lowrange to merely held the pressure.

Also, as previously mentioned, more than two pumping chambers can beutilized and a device having two chambers has been illustrated merelyfor purposes of clarity and simplicity.

The structure disclosed herein describes a iiuid control systemcomprising a pump having at least two pumping chambers or a structurehaving a plurality of pumps with each pump having single or multiplepumping chambers wherein control means is provided to allow selectivecornmunication of the combined discharge of said pump or pumps with theinlet of one or more of said pumping chambers.

This control can be either pressure responsive or tlow responsive,depending upon the particular application which is required.

While the present invention has been described in connection withcertain specific embodiments, it is to be understood that Ithe foregoingdescription is merely exemplary and that the concept of this inventionis susceptible of numerous other modifications, variations, andapplications which will be apparent to persons skilled in the art. Theinvention is to be limited, therefore, only by the broad scope of theappended claims.

I claim:

l. A uid control system comprising means having a plurality of fiuidpumping chambers, a single pressure responsive valve, a workcommunicating means, each of said pumping chambers being provided withan intake means and 'a discharge means, said intake means being in uidcommunication with said valve and said discharge means Vbeing in iiuidcommunication with said valve and said work communicating means, meansin said valve being movable in response to the combined pressure of thefluid discharge of said pumping chambers and being movable to a positionto allow iiuid communication between said discharge means andA one ormore of said in- Itake means, one-way valve means interposed betweensaid one or :more intake means and the remaining of said intake meanspreventing fluid How from said one or more of said intake means to theremaining of said intake means, whereby at least a portion of said fluiddischarge from said pumping chambers is bypassed to said one or more ofsaid intake means.

2. A pumping device comprising la pump having a low capacity pumpingchamber and a high capacity pumping chamber, each of said pumpingchambers having an intake means and a discharge means, a iiuid reservoirin uid communication with said intake means of said pumping chambers,check valve means interposed between at least one of said intake meansof said pumping chambers and the remaining intake means of the remainingpumping chambers to prevent flow of tluid from said one intake means tosaid remaining intake means, a single control valve, said intake andsaid discharge means of said pumping chambers being in iluidcommunication with said control valve, means `in said control valve toallow uid communication between said `discharge means and said oneintake means, and a Work outlet chamber in iluid communication with saiddischarge means of said pumping chambers.

3. A iluid pump means comprising a multiplicity of pumping chambers,each of said pumping chambers having an intake means and a dischargemeans, a single control valve, said intake means and said dischargemeans communicating with said valve, a work outlet means in fluidcommunication with said discharge means, ow responsive means in saidvalve to selectively prevent uid communication between said intake means'and said discharge means and -to -allow selective uid communicationbetween one or more of said intake means and said discharge means upon asu'icient increase in fluid flow in said valve, and one-Way valve meansinterposed between said one or more intake means and the remaining ofsaid intake means preventing tluid ow from said one or more of saidintake means to the remaining of said intake means.

4. A uid control system comprising means having a plurality of pumpingchambers, each of said pumping chambers having an inlet means Iand adischarge means, reservoir means in fluid communication with said inletmeans, one-Way valve means interposed between said one or more inletmeans land the remaining of said inlet means to prevent ow from said oneor more of said inlet means to the remaining of said inlet means and tosaid reservoir, a single control valve i-n uid communication with saiddischarge means and pressure responsive means in said valve toselectively communicate said discharge means with one or more of saidinlet means.

5. A tluid control system comprising means having a plurality of pumpingchambers, each of said pumping chambers having an inlet means and ladis-charge means, reservoir means in uid communication with said inletmeans, one-way valve means interposed between said one or more inletmeans and the remaining of said inlet means to prevent ow from said oneor more of said inlet means to the remaining of said inlet means and tosaid reservoir, a single control valve in uid communication with saiddischarge means and ow responsive means in said valve to selectivelycommunicate said discharge means `with one or more of said inlet means.

References Cited in the tile of this patent UNITED STATES PATENTS1,814,857 Rosle July 14, 1931 2,377,556 Jeannin June 5, 1945 2,401,567Jeannin June 4, 1946 2,599,701 Eames June 10, 1952 2,780,172 Coar Feb.5, 1957 2,878,753 Adams et al Mar. 24, 1959 2,887,060 Adams et al May19, 1959 FOREIGN PATENTS 559,108 Great Britain Feb. 4, 1944 712,796Germany Oct. 25, 1941 1,108,743 France Iune 17, 1954

